John Yeld
8 August 2007
If you thought the drought that Cape Town experienced during the particularly dry summers of 2003 and 2004 was bad, count yourself lucky you weren't living in the Western Cape in the 1920s when it was really dry!
UCT botany professor and eminent scientist William Bond says the 1920s experienced the worst rainfall on record since the country's oldest private weather station, Mertenhof at the head of the Biedouw valley in the Cederberg, became operational in 1898.
"Cape Town was nearly brought to its knees in 2004, but in the 1920s, there was just nothing, year after year!" he said.
Professor Bond was speaking last week at the Fynbos Forum - the annual meeting of researchers, planners, managers, landowners and a range of other stakeholders involved in conservation in the Cape Floristic Region, simply called fynbos - where he gave details of research into the impact of drought on fynbos plants in the Agter-Cederberg area.
He noted that projected climate change impacts for the Western Cape include longer, drier summers, with very few days with adequate soil moisture for plant growth. Both fynbos and Succulent Karoo vegetation types were projected to be "dramatically" reduced.
But while climate change models were statistically sophisticated, they were "biologically naïve", Bond said.
"This is dodgy stuff! Plants are tricky things - what do we measure in plants (to predict their mortality in response to climate change)? Nobody has a clue, really. It's embarrassing We have an embarrassing shortage of data. At the moment anything goes."
Although the drought of 2003/4 had been one of the worst in the 100-year record, there had been far worse droughts in the 1920s, he said.
Exceptionally dry years included 1928, when only 33% of average rain fell, and 1927, with 37%. In some instances, there were intervals of 18, 20 and even more than 20 months without two consecutive months of even average rainfall during this time.
"Is there climate change now? Look at the 1920s!"
Some plant species were "very resistant" to drought and others were "very vulnerable", Bond said.
"Are all species equally affected by drought? No way!"
And it was "really complicated" because even species in the same genus were affected very differently by the drought. Their research results suggested that mountain fynbos occurring on rocky soils might be less vulnerable to future climate change than anticipated, although lowland fynbos on deeper soils was "at great risk".
However, the research project revealed lower overall plant mortality than might have been expected, Bond said.
"I think we may have exaggerated the impacts (of climate change), which is a great relief."
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